Sir George Mendel, the Father of Genetics, in middle nineteen century speculated a set of law to describe the inheritance of biological characters. The basic assumption of this law describes that each character in an organism is controlled by a factor known as "Trait" presently known as" Gene". A milestone came in biological sciences when Avery, MacLeod & McCarty in 1944 ,explained the molecular nature of Gene and described that Deoxyribonucleotide ( DNA) is genetic material and gave rise to new branch of biological science known as" Molecular Biology". For better understanding of Gene, its function & for its manipulation, we now turn into new technology to advance the modern biological sciences. This technology is termed as Recombinant DNA technology or Genetic Engineering. This technique includes the process of Gene cloning and as we all know the word cloning means" identical copy".

Basis steps in Gene cloning
Gene cloning is the process in which identical copies of a particular gene are manufactured by utilizing molecular biology tools. Gene cloning method requires DNA vector which is small, circular DNA molecule present in bacteria and this DNA vector has natural talent to replicate with fidelity when gene or segment of DNA is inserted into these molecules with in host. Plasmid of bacterium, many plant and animal viruses acts as DNA vector. Few basic steps regarding Gene Cloning are as follows:

Step 1: Gene that is to be cloned is inserted into DNA vector using a class of manipulation enzymes known as Restriction endonuclease which cuts at specific site on DNA and DNA ligase which is required to join the DNA. This type of DNA is known as Recombinant
Step 2: The Recombinant DNA molecule get transformed into host which is usually bacterium.
Step 3: Within the host the Recombinant DNA molecule replicate producing clones of genes that is inserted into vector.
Step 4: When host cells divides, each cell contains numerous number of Recombinant DNA molecules. This is way by which inserted gene are amplified.

Gene cloning starts the new age of modern Bio-Technology. Gene cloning is being used to address problem in all areas of agriculture production, Pharmacology, Environmental issues, Food and nutrition field etc. This method makes DNA sequencing more effective and rapid as the massive genome sequence project like Human Genome Sequence Project was completed in the year 2000.

Application of Gene cloning
This recombinant DNA technology revolution opens the wide range of methods to solve problems in medicinal field. This technique is used to detect the genes which are responsible for genetic disorder and this disorder can be corrected by "Gene therapy". Gene therapy is emerging as promising and potential cure for treatment of cancer.

Gene cloning technique is going to acquire vital position to produce many recombinant pharmaceuticals like human insulin, recombinant DNA vaccine, recombinant human growth hormone, recombinant factor 8, interferon and many recombinant human proteins. There have been attempts to use gene cloning to disturb the infection cycle of many human pathogen like AIDS virus (HIV).

As this technology touches every aspects of our life how can agricultural be left behind. This technology is also securing good position in improving crop yields, production of herbicides resistant plants, drought resistant plants, disease resistant plants.

Gene library of an organism is prepared by gene cloning. Gene library is a collection of clones sufficient in number to be likely to contain every single gene present in a particular organism.

Gene library can be prepared by taking total cell DNA. The total cell DNA is partially digested with restriction end nuclease. This digested DNA is cloned into suitable vector. These recombinant vectors are transformed into particular host where they replicate and produce clone of genes present in that organism. This gene library is used detect the function, structure of gene of our interest present in particular organism.

The medicinal biology and the agricultural field are not the only way in which gene cloning are being utilized, an emerging field known as Archeogenetics is also obtaining benefits from this technology. By examine DNA sequence in living being and fossil, archeologist has begun to understand the evolutionary origin of modern humans.

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